By Jimmy Rogers
Many first-time native gardeners start their journey at a local hardware store or garden center. In July, one might find a display of purple coneflower and Mercury Rising coreopsis, both labeled as native and promising visitation by bees and butterflies. The purple coneflower has broad leaves beneath wide, purple flowers and the coreopsis has a cloud of thin leaves topped with blood-red flowers. It seems like a cartload of these plants is a ready-made native garden, complete with varying texture and flower color.
There is something wrong with this picture, however. For those of us in Laurel, these are not precisely native plants. In this article, we’ll define some terms, talk through a little ecology and provide some excellent resources for verifying and choosing native plants for your garden.
How Do We Define a Native Plant?
According to the National Wildlife Federation, “a plant is considered native if it has occurred naturally in a particular region, ecosystem, or habitat without human introduction.” To assess a given plant, then, we need to know where we are. State boundaries are helpful to a degree, but plants will often cross these lines. Many gardeners will be familiar with the USDA Plant Hardiness Zone designations (Laurel is in 7a), which slice the country up horizontally into temperature ranges. These zones are useful for guessing which crops and non-native ornamental plants will survive but tell us nothing about whether a plant is native to a particular zone.
Fortunately, we can organize the map with ecoregions. These are regions where the ecosystem and environment are fairly consistent. Here in Laurel, we straddle two ecoregions: the Maryland piedmont to the west of I-95, and the Maryland coastal plain to the east. When you’re searching for native plants, these terms serve as keys to unlock whether a plant is native or non-native.
Let’s look again at our two garden center plants and see if they’re native to Laurel. If we search for purple coneflower (Echinacea purpurea) on the Maryland Plant Atlas (marylandplantatlas.org), we see that while it occurs naturally in Illinois prairies, it’s non-native in Maryland. Researching Mercury Rising coreopsis is a little more challenging. After some googling, I found that Mercury Rising is a cultivar of pink coreopsis (Coreopsis rosea). Pink coreopsis is considered native (if rare) in the coastal plain ecoregion. Does that mean the cultivar is native and beneficial, too?
A cultivar is any variety of plant with desirable traits that humans have encouraged through selective breeding. In the world of native plants, these can most easily be identified by quotes around an appealing name, such as Mercury Rising. In the case of pink coreopsis, the flowers are typically pale pink in the straight species, and growers have selected for a dark red mutant flower.
If you’re a part of the native gardening community, native cultivars, or nativars, are a hot topic. There are concerns that changes to wild plant attributes can disrupt the relationships a plant has with native insects. If the color of foliage changes, does that mean an insect that eats the leaves will find it toxic? If a flower’s color changes, will its specialist bee be able to find it, and is the pollen still nutritious? Not all of these questions have been studied thoroughly, but when entomologists run experiments, they find that some cultivars do seem to disrupt these ancient relationships.
So, we’ve established that confirming if a plant is native can be complicated. Is all of this research worth the effort?
The best reason to choose native plant species is to garden for wildlife. With so much habitat disrupted or destroyed in the last century, sharing a little bit of your space with our wildlife is both impactful and easy. When we plant native plants in our gardens, we invite largely invisible insects to chew on those plants, and, in turn, provide critical prey for our birds and other animals. If we choose almost-native species or almost-functional plants (ecologically speaking), we may feel better about our choices, but we may not be making a real impact.
How to Select Species
Now that we know the terminology and a little bit of the ecology, let’s select some plants.
First, take a look at your garden bed and identify whether it gets full sun, full shade or falls somewhere in between (part sun). Next, assess whether the ground is usually dry, a little moist or usually wet. Lastly, let’s consider what habitat we can mimic. Does your garden most resemble a meadow (lots of sun, few trees, either wet or dry soil), a woodland (at least some trees, often with leaves covering the ground) or a wetland (where the ground is very wet, or even flooded, much of the time)? These are all keywords to remember.
To choose plants, you’ll need a plant listing for your region. For the Chesapeake Bay watershed, the U.S. Fish & Wildlife Service’s “Native Plants for Wildlife Habitat and Conservation Landscaping” guide is an excellent list categorized by ecoregion, habitat and degrees of sun and moisture. The guide also includes useful details for designing, such as height, flower color and bloom time. Helpfully, the Alliance for the Chesapeake has turned the list into a searchable database on nativeplantcenter.org.
